ghsa-63vm-hcp4-j9j3
Vulnerability from github
Published
2024-08-17 12:30
Modified
2024-08-22 18:31
Severity ?
5.5 (Medium) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Details

In the Linux kernel, the following vulnerability has been resolved:

bpf: Fix null pointer dereference in resolve_prog_type() for BPF_PROG_TYPE_EXT

When loading a EXT program without specifying attr->attach_prog_fd, the prog->aux->dst_prog will be null. At this time, calling resolve_prog_type() anywhere will result in a null pointer dereference.

Example stack trace:

[ 8.107863] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000004 [ 8.108262] Mem abort info: [ 8.108384] ESR = 0x0000000096000004 [ 8.108547] EC = 0x25: DABT (current EL), IL = 32 bits [ 8.108722] SET = 0, FnV = 0 [ 8.108827] EA = 0, S1PTW = 0 [ 8.108939] FSC = 0x04: level 0 translation fault [ 8.109102] Data abort info: [ 8.109203] ISV = 0, ISS = 0x00000004, ISS2 = 0x00000000 [ 8.109399] CM = 0, WnR = 0, TnD = 0, TagAccess = 0 [ 8.109614] GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 [ 8.109836] user pgtable: 4k pages, 48-bit VAs, pgdp=0000000101354000 [ 8.110011] [0000000000000004] pgd=0000000000000000, p4d=0000000000000000 [ 8.112624] Internal error: Oops: 0000000096000004 [#1] PREEMPT SMP [ 8.112783] Modules linked in: [ 8.113120] CPU: 0 PID: 99 Comm: may_access_dire Not tainted 6.10.0-rc3-next-20240613-dirty #1 [ 8.113230] Hardware name: linux,dummy-virt (DT) [ 8.113390] pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) [ 8.113429] pc : may_access_direct_pkt_data+0x24/0xa0 [ 8.113746] lr : add_subprog_and_kfunc+0x634/0x8e8 [ 8.113798] sp : ffff80008283b9f0 [ 8.113813] x29: ffff80008283b9f0 x28: ffff800082795048 x27: 0000000000000001 [ 8.113881] x26: ffff0000c0bb2600 x25: 0000000000000000 x24: 0000000000000000 [ 8.113897] x23: ffff0000c1134000 x22: 000000000001864f x21: ffff0000c1138000 [ 8.113912] x20: 0000000000000001 x19: ffff0000c12b8000 x18: ffffffffffffffff [ 8.113929] x17: 0000000000000000 x16: 0000000000000000 x15: 0720072007200720 [ 8.113944] x14: 0720072007200720 x13: 0720072007200720 x12: 0720072007200720 [ 8.113958] x11: 0720072007200720 x10: 0000000000f9fca4 x9 : ffff80008021f4e4 [ 8.113991] x8 : 0101010101010101 x7 : 746f72705f6d656d x6 : 000000001e0e0f5f [ 8.114006] x5 : 000000000001864f x4 : ffff0000c12b8000 x3 : 000000000000001c [ 8.114020] x2 : 0000000000000002 x1 : 0000000000000000 x0 : 0000000000000000 [ 8.114126] Call trace: [ 8.114159] may_access_direct_pkt_data+0x24/0xa0 [ 8.114202] bpf_check+0x3bc/0x28c0 [ 8.114214] bpf_prog_load+0x658/0xa58 [ 8.114227] __sys_bpf+0xc50/0x2250 [ 8.114240] __arm64_sys_bpf+0x28/0x40 [ 8.114254] invoke_syscall.constprop.0+0x54/0xf0 [ 8.114273] do_el0_svc+0x4c/0xd8 [ 8.114289] el0_svc+0x3c/0x140 [ 8.114305] el0t_64_sync_handler+0x134/0x150 [ 8.114331] el0t_64_sync+0x168/0x170 [ 8.114477] Code: 7100707f 54000081 f9401c00 f9403800 (b9400403) [ 8.118672] ---[ end trace 0000000000000000 ]---

One way to fix it is by forcing attach_prog_fd non-empty when bpf_prog_load(). But this will lead to libbpf_probe_bpf_prog_type API broken which use verifier log to probe prog type and will log nothing if we reject invalid EXT prog before bpf_check().

Another way is by adding null check in resolve_prog_type().

The issue was introduced by commit 4a9c7bbe2ed4 ("bpf: Resolve to prog->aux->dst_prog->type only for BPF_PROG_TYPE_EXT") which wanted to correct type resolution for BPF_PROG_TYPE_TRACING programs. Before that, the type resolution of BPF_PROG_TYPE_EXT prog actually follows the logic below:

prog->aux->dst_prog ? prog->aux->dst_prog->type : prog->type;

It implies that when EXT program is not yet attached to dst_prog, the prog type should be EXT itself. This code worked fine in the past. So just keep using it.

Fix this by returning prog->type for BPF_PROG_TYPE_EXT if dst_prog is not present in resolve_prog_type().

Show details on source website

To clipboard 

{
  "affected": [],
  "aliases": [
    "CVE-2024-43837"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-476"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2024-08-17T10:15:09Z",
    "severity": "MODERATE"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fix null pointer dereference in resolve_prog_type() for BPF_PROG_TYPE_EXT\n\nWhen loading a EXT program without specifying `attr-\u003eattach_prog_fd`,\nthe `prog-\u003eaux-\u003edst_prog` will be null. At this time, calling\nresolve_prog_type() anywhere will result in a null pointer dereference.\n\nExample stack trace:\n\n[    8.107863] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000004\n[    8.108262] Mem abort info:\n[    8.108384]   ESR = 0x0000000096000004\n[    8.108547]   EC = 0x25: DABT (current EL), IL = 32 bits\n[    8.108722]   SET = 0, FnV = 0\n[    8.108827]   EA = 0, S1PTW = 0\n[    8.108939]   FSC = 0x04: level 0 translation fault\n[    8.109102] Data abort info:\n[    8.109203]   ISV = 0, ISS = 0x00000004, ISS2 = 0x00000000\n[    8.109399]   CM = 0, WnR = 0, TnD = 0, TagAccess = 0\n[    8.109614]   GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0\n[    8.109836] user pgtable: 4k pages, 48-bit VAs, pgdp=0000000101354000\n[    8.110011] [0000000000000004] pgd=0000000000000000, p4d=0000000000000000\n[    8.112624] Internal error: Oops: 0000000096000004 [#1] PREEMPT SMP\n[    8.112783] Modules linked in:\n[    8.113120] CPU: 0 PID: 99 Comm: may_access_dire Not tainted 6.10.0-rc3-next-20240613-dirty #1\n[    8.113230] Hardware name: linux,dummy-virt (DT)\n[    8.113390] pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)\n[    8.113429] pc : may_access_direct_pkt_data+0x24/0xa0\n[    8.113746] lr : add_subprog_and_kfunc+0x634/0x8e8\n[    8.113798] sp : ffff80008283b9f0\n[    8.113813] x29: ffff80008283b9f0 x28: ffff800082795048 x27: 0000000000000001\n[    8.113881] x26: ffff0000c0bb2600 x25: 0000000000000000 x24: 0000000000000000\n[    8.113897] x23: ffff0000c1134000 x22: 000000000001864f x21: ffff0000c1138000\n[    8.113912] x20: 0000000000000001 x19: ffff0000c12b8000 x18: ffffffffffffffff\n[    8.113929] x17: 0000000000000000 x16: 0000000000000000 x15: 0720072007200720\n[    8.113944] x14: 0720072007200720 x13: 0720072007200720 x12: 0720072007200720\n[    8.113958] x11: 0720072007200720 x10: 0000000000f9fca4 x9 : ffff80008021f4e4\n[    8.113991] x8 : 0101010101010101 x7 : 746f72705f6d656d x6 : 000000001e0e0f5f\n[    8.114006] x5 : 000000000001864f x4 : ffff0000c12b8000 x3 : 000000000000001c\n[    8.114020] x2 : 0000000000000002 x1 : 0000000000000000 x0 : 0000000000000000\n[    8.114126] Call trace:\n[    8.114159]  may_access_direct_pkt_data+0x24/0xa0\n[    8.114202]  bpf_check+0x3bc/0x28c0\n[    8.114214]  bpf_prog_load+0x658/0xa58\n[    8.114227]  __sys_bpf+0xc50/0x2250\n[    8.114240]  __arm64_sys_bpf+0x28/0x40\n[    8.114254]  invoke_syscall.constprop.0+0x54/0xf0\n[    8.114273]  do_el0_svc+0x4c/0xd8\n[    8.114289]  el0_svc+0x3c/0x140\n[    8.114305]  el0t_64_sync_handler+0x134/0x150\n[    8.114331]  el0t_64_sync+0x168/0x170\n[    8.114477] Code: 7100707f 54000081 f9401c00 f9403800 (b9400403)\n[    8.118672] ---[ end trace 0000000000000000 ]---\n\nOne way to fix it is by forcing `attach_prog_fd` non-empty when\nbpf_prog_load(). But this will lead to `libbpf_probe_bpf_prog_type`\nAPI broken which use verifier log to probe prog type and will log\nnothing if we reject invalid EXT prog before bpf_check().\n\nAnother way is by adding null check in resolve_prog_type().\n\nThe issue was introduced by commit 4a9c7bbe2ed4 (\"bpf: Resolve to\nprog-\u003eaux-\u003edst_prog-\u003etype only for BPF_PROG_TYPE_EXT\") which wanted\nto correct type resolution for BPF_PROG_TYPE_TRACING programs. Before\nthat, the type resolution of BPF_PROG_TYPE_EXT prog actually follows\nthe logic below:\n\n  prog-\u003eaux-\u003edst_prog ? prog-\u003eaux-\u003edst_prog-\u003etype : prog-\u003etype;\n\nIt implies that when EXT program is not yet attached to `dst_prog`,\nthe prog type should be EXT itself. This code worked fine in the past.\nSo just keep using it.\n\nFix this by returning `prog-\u003etype` for BPF_PROG_TYPE_EXT if `dst_prog`\nis not present in resolve_prog_type().",
  "id": "GHSA-63vm-hcp4-j9j3",
  "modified": "2024-08-22T18:31:20Z",
  "published": "2024-08-17T12:30:32Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2024-43837"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/9d40fd516aeae6779e3c84c6b96700ca76285847"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b29a880bb145e1f1c1df5ab88ed26b1495ff9f09"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f7866c35873377313ff94398f17d425b28b71de1"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/fcac5feb06f31ee4c88bca9bf98d8bc3ca7d2615"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}


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